A vacuum packing machine is formed with an upper case and a lower case being hinge-coupled, and performs vacuum-packing through a vacuum wrapper being placed between the upper case and the lower case and the cases being closed.
In the related art chamber-type vacuum packing machine, an opening portion of a wrapper to be vacuumized is placed in a vacuum chamber, and air within the vacuum chamber is withdrawn therefrom by using a vacuum pump, or the like, to vacuumize the interior of the wrapper.
When vacuum packing using the vacuum pump, or the like, is completed, the opening portion of the wrapper is heat-fused and sealed by hot wires positioned in the upper and lower cases, completing packing. This structure is described in detail in Korean Utility Model Registration No. 20-0319700, and the like.
Meanwhile, in case of vacuum-packing a food item or food ingredients containing moisture to some extent, moisture contained in the food item or food ingredients, or the like, is withdrawn together with air, and a partial amount of moisture withdrawn through the foregoing process may be withdrawn into the vacuum pump together with air, while a remaining amount of moisture may be gathered in the chamber.
The moisture gathered in the chamber may stagnate or bacteria (or germs) may propagate therein with the passage of time. Vacuum-packing a new food item or food ingredients with contaminated moisture remaining in the chamber may not be sanitary. In addition, during vacuum-packing, moisture present within the chamber may be withdrawn into the vacuum pump through a vacuum intake to damage the vacuum pump, resulting in a breakdown of the vacuum packing machine.
Meanwhile, a pressure sensor, an element for measuring pressure in a process or a system, is a sensor having various purposes and which is used extensively, such as in industrial measurement, automatic control, in the medical field, vehicle engine control, environmental control, in electric products, and the like.
A measurement principle of a pressure sensor uses displacement, deformation, a magnetic-thermal conduction rate, an amount of vibrations, and the like, and various types of pressure sensors have been put to practical use.
Pressure sensors include a mechanical pressure sensor using a Broudon Tube, a diaphragm, a bellows, and the like, an electromagnetic pressure sensor having a portion thereof for converting a mechanical displacement into an electrical signal, a semiconductor-type pressure sensor, and the like.
FIG. 13 illustrates an example of a mechanical pressure sensor measuring air pressure.
The pressure sensor illustrated in FIG. 13 has a function of generating an electrical signal to interrupt a current or to allow a current to flow, at a particular pressure.
Referring to FIG. 13, in the related art pressure sensor, a sealing member 60 is installed in an internal space between a lower housing 10 and an upper housing 70, and a conductive member 50 having electrical conductivity is attached below the sealing member 60. For example, the conductive member 50 may be attached to the sealing member 60 as an insertion protrusion (not shown) of the sealing member 60 is inserted into a connection hole 51 formed in the center of the conductive member 50.
An elastic member 40 having a coil spring shape and providing elastic force to the conductive member 50 and the sealing member 60 is disposed above the lower housing 10.
Also, a pair of connection members 20 are installed in a penetrating manner and are electrically connected to the conductive member 50 when the conductive member 50 descends in response to elastic force of the elastic member 40. In this case, in order to make heights of the connection members 20 uniform when in contact with the conductive member 50, the connection members 20 are exposed from the lower housing 10 through insertion protrusions formed to be protruded from an upper portion of the lower housing 10.
The sealing member 60 cuts off air flow between lower and upper sides thereof, and the upper housing 70 has an air flow hole 71 formed therein to allow ambient air to be introduced to an upper space of the sealing member 60.
The related art pressure sensor may be used to measure air pressure, and an operation thereof in a case in which an air intake operation is performed by using a vacuum pump in a vacuum packing machine, a vacuum processor, a vacuum chamber, and the like will be described.
In the pressure sensor, an air inlet tube 11 is connected to a vacuum line in which a vacuum operation is performed. When air is withdrawn by a vacuum pump (not shown), air present in the space between a lower side of the sealing member 60 and the lower housing 10 is withdrawn out to lower pressure.
As pressure in the space is lowered, the sealing member 60 descends, while overcoming elastic force of the elastic member 400, and when pressure in the space reaches a pre-set pressure level, the conductive member 50 attached to a lower portion of the sealing member 60 comes into contact with the connection members 20.
Accordingly, the pair of connection members 20 are electrically connected to transmit an electrical signal outwardly. On the basis of the electrical signal, an operation of the vacuum pump (not shown) may be stopped.
In this manner, in the related art pressure sensor, when air pressure in the vacuum line is lowered to below a predetermined pressure level, an electrical signal is transmitted to stop an operation of the vacuum pump.
Meanwhile, when the operation of the vacuum pump is stopped after the vacuum operation is completed, or when ambient air is introduced to the vacuum line because a vacuum operation is not performed, the sealing member 60 descends to release contact between the conductive member 50 and the connection members 20.
In this case, since the vacuum line and the interior of the pressure sensor communicate to allow air to flow therein, moisture, foreign objects, and the like, may thus be introduced to the interior of the pressure sensor. The introduction of moisture, and the like, may frequently occur when a vacuum state within the pressure sensor is abruptly released and ambient air is rapidly introduced thereto.
When moisture, foreign objects, and the like, are introduced to the interior of the pressure sensor, descending of the sealing member 60 may be interfered with or contact between the connection members 20 and the conductive member 50 may be defective, resulting in complete loss of the function of the pressure sensor.
The problem in which moisture, foreign objects, are introduced to the interior of the pressure sensor is not limited to a pressure sensor that reacts under particular pressure as illustrated FIG. 13, and may also arise in the same manner even in a pressure sensor for measuring pressure in a predetermined range.
Also, a pressure sensor for measuring air pressure, including an electric pressure sensor, as well as a mechanical pressure sensor, may have the foregoing problem.
In order to address the problem, Korean Patent Laid-Open Publication. No. 2009-31180 discloses a technique of preventing moisture or foreign objects being introduced through a separate membrane member, or the like, but such a configuration requires additional components, making the configuration complicated and making it difficult to assemble the components.
Thus, a technique capable of guaranteeing a stable operation of a pressure sensor, which has a simple configuration and is easily assembled so as to be commonly used in a vacuum packing machine, or the like, to measure air pressure, by preventing the introduction of moisture or foreign objects into the interior of the pressure sensor, is required.